Circuit Breaker

We can use a circuit breakers to limit the current in a single circuit in most household applications. Although breakers come in many sizes, typically a single circuit is limited to 20 amperes. This means that to bend it downward and release the spring-loaded trip-lever, 20 amps of current will heat the bimetallic strip.

Another mechanism is employed to handle large surges from a short circuit since the heating is fairly slow. The bimetallic strip is pulled down by a small electromagnet consisting of wire loops around a piece of iron in case of a large current surge. [Diagram Source: C.R. Nave, Hyper Physics]